Dry matter intake and weight gain of West African dwarf sheep fed Pennisetum purpureum substituted with leaves of mulberry (Morus alba)

A N Fajemisin and O B Omotoso

Department of Animal Production and Health, School of Agriculture and Agricultural Technology, Federal University of Technology, P M B 704, Akure, Ondo State, Nigeria
obomotoso@futa.edu.ng

Abstract

A sixty-three day study with twenty West African Dwarf (WAD) sheep aged 8-9 months with average live weight of 9.98±0.21kg was carried out to determine feed intake and weight gain when a sole diet of fresh forage of Pennisetum purpureum was replaced at five levels (0, 25, 50, 75 and 100%) with fresh leaves of mulberry (Morus alba). The sheep were divided into 5 groups of four sheep per group housed in individual pens in a completely randomized design.

There were linear or curvilinear increases in feed DM intake and in live weight gain, with related improvement in feed conversion, as mulberry leaves replaced. P. purpureum forage in the diet. It was hypothesized that the effect of the increasing levels of mulberry leaves replacing the grass was due to: (i) the increased supply of amino acids from the “bypass” protein in the mulberry leaves; and (ii) of glucose precursors derived from a proportion of the absorbed amino acids plus the increase in rumen propionate from the expected reduction in rumen methane as the dietary concentration of mulberry leaves increased.

Keywords: bypass protein, glucose precursors, methane, propionate, tannin

Introduction

The major constraint to ruminant production in developing countries like Nigeria is the scarcity or fluctuating quantity and quality of year-round forage supply. The natural pastures and crop residues available for animals after crop harvest are fibrous and low in most essential nutrients which are required for rumen microbial fermentation and performance of the host animal (Ahamefule et al 2006). This is manifested in loss of weight, reduced reproduction capacity and increased mortality. These problems have led animal nutritionists to focus attention on nutritious tree foliages such as mulberry (Mora alba) which is available throughout the season (Fajemisin 2017).

Pennisetum purpureum

Schumach is a robust perennial grass that has been widely used as tropical forage, with higher dry matter (DM) yield than other tropical grasses (Hanna et al 2004). Although, it has low protein concentration, it can provide a satisfactory forage source for ruminants if supplemented with legumes and protein-rich concentrates (Nyambati et al 2003). Mulberry is a shrub or tree traditionally used in sericulture in various countries. It originated from four main species, the White mulberry (Morus alba ), the Lu mulberry (M. multicaulis), the Mountain mulberry ( M. bombycis) and the Guangdong Mulberry (M. atropurpurea ). The White Mulberry belongs to the order Urticales, the family Moraceae and the genus Morus. The most common of the species is White Mulberry (Morus nigra). After evaluating the nutritive value of this plant, Prasad and Reddy (1991) concluded that mulberry is an excellent feed for high yielding animals and can be offered fresh or dried in compound feeds. Fajemisin (2017) also showed that mulberry foliage could be used as a supplement to poor quality forages or as the main component of the diet in livestock production systems.

This study was designed to evaluate the effect of substituting forage ofPennisetum purpureum with leaves of white mulberry on feed intake, nitrogen metabolism and weight gain of West African Dwarf sheep.

Materials and methods

Description of the study area

The experiment was carried out at the small ruminants unit of Teaching and Research (T&R) Farm, Department of Animal Production and Health, Federal University of Technology, Akure (FUTA), Ondo State, Nigeria.

Collection and processing of the forages

Pennisetum purpureum leaves were harvested from the pasture site on the T&R Farm of FUTA while the mulberry was harvested from the pasture site of Ondo State Sunshine Agro-based Empowerment Centre, Wealth Creation Agency, Ondo Road, Akure. The foliage was collected in the evenings on daily basis and air-dried before use the following day.

Experimental design

Twenty West African Dwarf (WAD) sheep aged 8-9 months with live weight of 9.98±0.21 kg were selected from the sheep unit of the T&R Farm. They were vaccinated against Pesté-Petit dé Ruminanté (PPR / kata) using Rinderpest Tissue Culture vaccine. Treatment against endo- and ecto-parasites using Ivermectin (1 ml per 20 kg body weight of animal subcutaneously) and they were also drenched with Albendazole ®. The sheep were housed individually in pens. An acclimatization period of 7 days was allowed before commencement of data collection.

Five diets were formulated such that Pennisetum purpureum was substituted with white Mulberry leaves (DM basis) as: ML0 (100% Pennisetum purpureum), ML25 (75% Pennisetum purpureum + 25% Mulberry leaves), ML50 (50% Pennisetum purpureum + 50% Mulberry leaves), ML75 (25% Pennisetum purpureum + 75% Mulberry) and ML100 (100% Mulberry leaves). Twenty West African Dwarf sheep (four sheep per treatment) were balanced for weight and randomly assigned to the diets ina Completely Randomized Design for a period of 63 days. The diets were thoroughly mixed and fed ad libitum to the sheep.

Data collection, feed analysis and data analysis

Feed intake of sheep was estimated as the difference between daily feed offered and residues. The sheep were weighed before the commencement of experiment and weekly in the morning before feeding. Samples of feed were analyzed for chemical composition using the methods of AOAC (2002) and Van Soest et al (1991). All data generated were subjected to analysis of variance (ANOVA) using SAS (2010)version 9.3.

Results

The crude protein percentage in the diets increased and the crude fibre decreased as P. purpureum was replaced by mulberry leaves (Table 1).

There were linear or curvilinear increases in DM feed intake and growth rate (Figures 1 and 2) with related improvement in DM feed conversion (Figure 3) as mulberry leaves replaced . P. purpureum (original data in Table 2).

Figure 1. DM feed intake by WAD sheep fed P. purpureum substituted with mulberry leaves	Figure 2. Live weight gain by WAD sheep fed P. purpureum substituted with mulberry leaves

Figure 3. DM feed conversion by WAD sheep fed P. purpureum substituted with mulberry leaves

Discussion

The control diet of 100% P. purpureum was marginally low in crude protein (11.4% in DM) whereas diets with increasing substitution by mulberry leaves had crude protein levels rising from 13.7 to 23% in DM. The linear increase in growth rate due to increasing level of mulberry leaves in the diet is not thought to be because of increased crude protein levels per se but rather to the nature of the protein: (i) as being mostly in the form of “true” protein; and (ii) through its association with phenolic compounds (eg: condensed tannin) that protect it from microbial attack in the rumen (Barry and McNabb 1999), thus facilitating the rumen escape/bypass of the protein for more efficient enzymic digestion in the intestine (Preston and Leng 1987). It is also probable that the increasing proportion of mulberry leaves replacing the P. purpureum would result in reduced rumen methane production following reports from Maselema and Chigwa (2017) and Preston et al (2019) that in vitro rumen methane was higher in grasses than in leaves from trees and shrubs.

The effect of the increasing levels of mulberry leaves in the diet would thus be due to increased supply of: (i) amino acids from the “bypass” protein; and (ii) glucose precursors derived from a proportion of the absorbed amino acids plus the increase in propionate resulting from the expected reduction in rumen methane. The net result from mulberry leaves replacing P. purpureum would this be an increase in growth rate and improved feed conversion as was observed in the experiment reported in this paper.

Conclusions

• There were increases in feed DM intake and growth rate, with related improvement in feed conversion, as mulberry leaves replaced. P. purpureum forage in the diet of West African Dwarf sheep.
  
  
• It is hypothesized that the benefits from the increasing levels of mulberry leaves replacing P. purpureum were due to the increased supply of: (i) amino acids from the “bypass” protein in the mulberry leaves; and (ii) glucose precursors derived from a proportion of the absorbed amino acids plus the increase in rumen propionate resulting from the expected reduction in rumen methane from the mulberry leaves.
  
  
• The net result from mulberry leaves replacing P. purpureum would this be a linear increase in growth rate and improved feed conversion as was observed in the experiment reported in this paper.

References

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Received 18 January 2020; Accepted 2 February 2020; Published 2 March 2020

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